Solid, heterogeneous catalysts and methods of use

ABSTRACT

Solid mixed catalysts and methods for use in conversion of triglycerides and free fatty acids to biodiesel are described. A batch or continuous process may be used with the catalysts for transesterification of triglycerides with an alkyl alcohol to produce corresponding mono carboxylic acid esters and glycerol in high yields and purity. Similarly, alkyl and aryl carboxylic acids and free fatty acids are also converted to corresponding alkyl esters. The described catalysts are thermostable, long lasting, and highly active.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/059,932, entitled “SOLID, HETEROGENEOUS CATALYSTS AND METHODS OFUSE,” filed Apr. 12, 2011, which is the national phase under 35 U.S.C.§371 of PCT International Application No. PCT/CA2009/001165 with anInternational Filing Date of Aug. 20, 2009, which claims the priority ofU.S. Provisional Patent Application No. 61/090,781 filed Aug. 21, 2008,all of which are incorporated by reference herein, in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to the production of biodieselfrom triglycerides and free fatty acids. More particularly, the presentinvention relates to solid, heterogeneous catalysts for use in theproduction of biodiesel.

BACKGROUND OF THE INVENTION

Biodiesel is a non-toxic fuel that may be used alone or blended withpetroleum diesel at any ratio to create a biodiesel blend. Biodiesel hasa high octane number, is essentially free of sulfur and aromatics, andis therefore a clean burning fuel, free of NOx and SOx.

Biodiesel is commonly produced by transesterification, the reaction ofan alcohol with triglycerides present in animal fat or vegetable oil.Generally, such reactions are catalyzed by homogeneous catalysts such asmineral acids, metal hydroxide, metal alkoxides, and carbonates. Asmineral acid catalyzed reactions are slow and therefore economicallynon-viable, metal hydroxides such as sodium or potassium hydroxides aremore commonly used as they are relatively inexpensive and suitablyeffective. One disadvantage to using alkaline hydroxides or carbonatesin transesterification reactions is the generation of soap as a reactionbyproduct. The generation of soap compromises product yields and productquality. Glycerol (glycerine) is also produced as a byproduct, howeverthe presence of water and soaps creates an emulsion that complicates thepurification of biodiesel and the separation of glycerol from the fattyacid esters. Generally, copious amounts of acids and water are used toneutralize catalyst and remove soaps from the desirable reactionproducts. As a result, the increased number of steps required to obtainpurified biodiesel and useable quality glycerol add tremendously to thecost of production, and also lead to a certain degree of environmentalpollution.

The following equations illustrate the reactions that take place duringtransesterification to biodiesel by existing methods, using homogeneouscatalysts.

Further attempts have been made in the prior art to replace homogeneouscatalysts with solid catalysts. Such replacement of homogeneouscatalysts, for example with solid metal oxides and double metalcyanides, is perceived to have the advantages of simple retrieval ofcatalyst, elimination of soap formation and reduction of environmentalpollutants. Further, the use of solid catalysts in place of homogeneouscatalysts may lead to higher-quality esters and glycerol, which are moreeasily separable and without added cost to refine the resulting ester(see for example U.S. Pat. No. 6,147,196 to Stern et al). In accordancewith this expectation, a number of solid catalysts have now beenreported in literature. These are generally based on metal oxides anddouble metal cyanides to effect the desired transesterification reactionshown in equation-5 below.

European patent EP-80-198-243 describes a solid, heterogeneous catalystthat is based on a mixture of iron oxide with alumina. This catalystrequires a very large catalyst to oil ratio, and extended contact timeof more than 6 hours. Reaction temperatures of 280° C. to 320° C. aretypically required, which results in coloration of the biodiesel andpresence of impurities.

U.S. Pat. No. 5,908,946 describes catalysts prepared from mixtures ofzinc oxide, and alumina zinc aluminate. While the catalyst does providecomplete conversion to methyl ester, long reaction times and hightemperatures are required. Moreover, the reaction is sensitive to waterand free fatty acids. When free fatty acid conversion is desired, anesterification step must be carried out prior to the transesterificationreaction.

U.S. Pat. No. 7,151,187 describes catalysts made by combining two ormore of titanium isopropoxide, zinc oxide, alumina, and bismuth saltsusing nitric acid. Use of nitric acid is not desirable, as it iscorrosive, toxic, and has a negative impact on the environment. Further,the use of nitric acid also impacts the basicity of the catalyst, whichmay affect the transesterification reaction.

It has further been shown that exchange of sodium ions in the 4 Åmolecular sieves (formula: Na₁₂[(AlO₂)₁₂(SiO₂)₁₂].xH₂O), with either K⁺or Cs⁺ leads to a material with higher basicity which is essential inheterogeneous transesterification catalysis. However, testing has shownthat despite enhancement of the basic sites, these ion-exchangedzeolites failed to achieve complete transformation of triglycerides tobiodiesel.

A double metal cyanide catalyst-Fe₂Zn₃(CN)₁₀ has also been shown totransesterify oils at relatively lower temperatures. However, the slowpace of reaction leads to extended reaction time and requires excessivecatalyst and reactor volume.

A suitable heterogeneous catalyst and method for complete transformationof triglycerides to biodiesel and for conversion of free fatty acids tocorresponding esters has not been described to date. Further, suchreactions do not appear to be currently possible under mild temperatureand pressure conditions, while minimizing reaction time and productpurification steps.

SUMMARY

In accordance with a first aspect of the invention, there is provided asolid, heterogeneous catalyst preparation for use in an esterificationor transesterification reaction, the mixed catalyst preparationcomprising at least one molecular sieve and at least one catalyst,wherein the catalyst comprises a metal oxide or double-metal cyanide.

In an embodiment, the metal oxide is aluminum oxide, calcium oxide,gallium oxide, hafnium oxide, iron oxide, lanthanum oxide, siliconoxide, strontium oxide, titanium oxide, zinc oxide, or zirconium oxide.The metal oxide may be formed by calcination of a metal hydroxide, forexample, aluminum hydroxide, calcium hydroxide, gallium hydroxide,hafnium hydroxide, iron hydroxide, lanthanum hydroxide, siliconhydroxide, strontium hydroxide, titanium hydroxide, zinc hydroxide, orzirconium hydroxide.

In an embodiment, the double-metal cyanide is of the general formulaFe₂M₃(CN)₁₀ wherein M is lanthanum, copper or aluminum.

In suitable embodiments, the molecular sieve may be of the type 3 Å, 4Å, or 5 Å, having the general formulaK_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, Na₁₂[(AlO₂)₁₂(SiO₂)₁₂].xH₂O) orCa_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, respectively. The molecularsieve may be, for example, a natural or synthetic zeolite. Preferably,the molecular sieve is a modified molecular sieve, modified to enhancethe basicity of the molecular sieve.

Suitable modified molecular sieves may have been modified to replace atleast one sodium ion within the molecular sieve with at least one metalcation. Suitable metal cations include K⁺, Cs⁺, and the like, resultingin a general formula of K_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,K_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂].xH₂O,Cs_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, orCs_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂].xH₂O, for example.

In various embodiments, any of the catalyst preparations may be providedin powdered, pelleted, extruded, and/or calcined form. The catalystremains heterogeneous during the reaction, and is generally recoverablefrom the reaction products by filtration.

In accordance with a second aspect of the invention, there is provided acatalyst of the molecular formula: x(La₂O₃).y(La(OH)₃).z(TiO₂) whereinx, y and z independently have a value between 1-2. Such catalyst may beprepared from lanthanum oxide or lanthanum hydroxide and titanium oxide,and these oxides may be prepared in situ.

In accordance with a third aspect of the invention, there is provided amodified molecular sieve of the general formulaK_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,K_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,Cs_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, orCS_(m)Ca_(n)Na_({12-(m+2n)})[AlO₂)₁₂(SiO₂)₁₂].xH₂O.

In accordance with a fourth aspect of the invention, there is provided acatalyst according to the formula a(La₂O₃).x(TiO₂).y(ZnO).z(MS), whereinA and X are each 1; Y is 1-2, Z is 3-4, and wherein MS is a molecularsieve of the general formula K_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,K_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,Cs_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, orCs_(m)Ca_(n)Na_({12-(m+2)})[(AlO₂)₁₂(SiO₂)₁₂].xH₂O.

In accordance with a fifth aspect of the invention, there is provided acatalyst according to the formula (Al₂O₃).(TiO₂).(ZnO).z(MS) wherein zis 10 and wherein MS is a molecular sieve of the general formulaK_(n)Na_((12-n))[(AlO₂)₁₂ (SiO₂)₁₂].xH₂O,K_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,Cs_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, orCs_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂ (SiO₂)₁₂].xH₂O.

In accordance with a sixth aspect of the invention, there is provided acatalyst according to the formula {(Fe₂M₃ (CN)₁₀}.Al₂O₃.TiO₂.ZnO. MS,wherein M is Cu, Al or La, and wherein MS is a molecular sieve of thegeneral formula K_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,K_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂].xH₂O,CS_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, orCs_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂].xH₂O.

In accordance with another aspect of the invention, there is provided amethod for effecting esterification or transesterification of a startingmaterial, comprising reacting the starting material with an alcohol inthe presence of a solid, heterogeneous catalyst as described above.

The starting material may be an oil, and/or may comprise triglycerides,free fatty acids, and/or carboxylic acids. The method may be used toproduce biodiesel and/or glycerol as a reaction product. Notably, insuitable embodiments, soap is not produced as a byproduct of thereaction.

In an embodiment, the reaction is conducted at temperatures between 150°C. and 250° C. Further, the reaction may be conducted at pressures lessthan 1000 psi. In various embodiments, the reaction may be conducted ina batch reactor or continuous reactor such as a fixed bed reactor. Thereaction may be conducted in two or more successive stages. In a fixedbed reactor, the reaction may be conducted with a ratio of 0.1-2.0volumes of injected oil/volume of catalyst per hour.

DESCRIPTION

Generally, the present invention provides solid, heterogeneous catalystsand methods for use in the production of alkyl esters from a startingmaterial containing any one or more of the following: triglycerides,free fatty acids, aromatic carboxylic acids, aliphatic carboxylic acids.

The terms “oil”, “feedstock”, and “starting material” as used hereinrefer to a substance having any detectable triglyceride and/or freefatty acid and/or carboxylic acid (whether aromatic or aliphatic)content, such as animal fats, vegetable oils, used cooking oils, and thelike. Examples of vegetable oils include, without limitation, canolaoil, corn oil, soybean oil, palm oil, coconut oil, jatropha oil,camolina oil, cottonseed oil, flax oil, sunflower oil, and rapeseed oil.Examples of animal fats include, without limitation, beef tallow, porklard, and the like. Other further starting materials may also beappropriate, such as triglycerides present in or obtained from certaintypes of algaes, etc.

The term “heterogeneous” as used herein with respect to solid catalysts,refers to any solid physical form of suitable catalyst, whether acatalyst is calcined or otherwise hardened, whether provided in powder,pellet, balled, or extruded form or anchored to a solid structure suchas a molecular sieve or natural or synthetic solid state composition.Such catalysts are generally not solubilized during the reaction and themajority of the catalyst is recoverable from the reaction products bysimple filtration.

Catalyst and Reaction Overview

Notably, the catalysts and methods may be used in the production of highyield, high purity biodiesel. Generally, the catalyst may be a metaloxide, or double metal cyanide, or mixtures of the foregoing. Thecatalysts are provided in solid form, for example in powdered, pelleted,or extruded form, supported on a solid structure such as a molecularsieve. The resulting catalysts are thermostable. For example, the metaloxide based catalysts described below are stable above 600° C., maintaina high level of activity even after prolonged use, provide excellentselectivity, and are insoluble in triglycerides and alkyl alcohols,preventing elution and volume loss. Further, these catalysts are notusually limited by reaction temperature and are highly tolerant of freefatty acids and water content during use.

Equations describing the general reactions are represented below inEquations 6 through 8.

In the above equations, R′, R″, and R′″ may be the same or different,and each may be a C₁ to C₂₂ linear or branched chain alkyl group, whichmay be further substituted with hydroxyl, alkoxy or halogens likechloro, bromo or fluoro or an aryl group that can be substituted withchloro, bromo, fluoro, nitro, lower alkoxy or lower alkyl such asmethyl, ethyl, propyl, isopropyl or butyl which may be furthersubstituted with halogens such as chloro, bromo fluoro or a phenyl groupthat can be substituted with chloro, bromo fluoro nitro, lower alkyl oralkoxy group. Further, each may represent an alkyl group of amonocarboxyllic acid such as acetic, propionic, butyric, caproic,caprilic, capric, lauric, myristic, palmitic, oleic, stearic or adicarboxylic acid such as adipic acid, which are in an ester form with aC1 to C18 monohydric aliphatic alcohol such as methyl, ethyl, propyl,isopropyl, butyl and stearyl alcohol, a monohydric aromatic alcohol suchas benzyl or substituted benzyl alcohol or a dihydric alcohol such asethylene glycol, propylene glycol, butane diol or a polyhydric alcoholsuch as glycerol, sorbitol, polyerythritol, polyethylene glycol and polypropylene glycol etc.

Further, ROH in equations 6 through 8 represents suitable alcohols,including without limitation: a C₁ to C₁₈ monohydric aliphatic alcoholsuch as methanol, ethanol, propanol, isopropanol, butyl alcohol, andstearyl alcohol; a monohydric aromatic alcohol such as benzyl alcohol ora substituted benzyl alcohol; a dihydric alcohol such as ethyleneglycol, propylene glycol, and butanediol; or a polyhydric alcohol suchas glycerol, sorbitol, polyerythritol, polyethylene glycol, andpolypropylene glycol. Other suitable alcohols may also be used, as willbe apparent to those of skill in the art.

Metal Oxide Catalysts

In equations 6 through 8, the catalyst may include an oxide of a metal,for example aluminum, calcium, cerium, gallium, hafnium, iron,lanthanum, magnesium, strontium, titanium, zirconium, or zinc. Suchmetal oxides or hydroxides may be used alone or in combination withsimilar or dissimilar catalysts, and the catalyst is provided in solidform. For example, the catalyst may be supported on a molecular sieve orzeolite, in which some of the sodium ions have been exchanged forpotassium or cesium ions. The catalysts may be provided as a powder,pellets, balls, or extruded forms, and calcined under vacuum or in thepresence of a neutral gas (such as argon, nitrogen, or helium) attemperatures between 200° C. to 1200° C., usually between 400° C. to800° C. Such oxides may be obtained commercially or prepared fromappropriate metal halide, hydroxide, or a metal nitrate.

Double Metal Cyanide Catalysts

In equations 6 through 8, the catalyst may include a double metalcyanide of the general formula Fe₂M₃(CN)_(n)(ROH).xM₂.yH₂O), where M isa metal, for example lanthanum, strontium, copper, aluminum, magnesiumcobalt and titanium. Values for x and y may range between 1 and 2. Suchcatalysts may be used alone or in combination with similar catalysts orwith the above-described metal oxide/hydroxide catalysts, with thecatalyst provided in solid form. For example, the catalyst may besupported on a molecular sieve or zeolite, in which some of the sodiumions have been exchanged for potassium or cesium ions. The catalysts maybe provided as a powder, pellets, balls, or extruded forms, and calcinedin the presence or absence of a neutral gas (such as argon, nitrogen, orhelium) at temperatures between 100° C. to 200° C., usually between 160°C. to 180° C.

Use of Molecular Sieves in Catalyst Preparation

The mixed catalyst may include a molecular sieve, for example a naturalor synthetic zeolite. Such substances may vary in composition andcrystal structure. The catalyst may, for example, be a titanium zeoliteprepared by exchange of silicon atoms with titanium atoms. Further, themolecular sieves may by of types 3 Å, 4 Å, and 5 Å. For example, type 3Å of formula K_(n)Na_(12-n)[(AlO₂)₁₂(SiO₂)₁₂].xH₂O), or type 4 Å offormula Na₁₂[(AlO₂)₁₂(SiO₂)₁₂].xH₂O), where n and x are integers. Themolecular sieve is first treated to exchange one or more of the existingsodium ions with potassium and cesium ions to produce enhanced basicsites. The resulting substance may be calcined in the presence orabsence of a neutral gas (such as nitrogen, argon, or helium) and may beused alone as a catalyst or as a solid support for the metaloxide/hydroxide and double metal cyanide catalysts described above.

Reaction Methods

The above-described catalysts may be used with equal efficiency in abatch, intermittent/semi continuous, or continuous mode at temperaturesbetween 200° C. and 225° C. and pressures up to 650 psi, depending onthe specific catalyst, starting material, and process chosen.

Fatty acid esters and glycerol products from the reactor are generallyof high purity, and the glycerol is colorless and high in quality.Quality of the reaction products may be further improved by treatmentwith activated charcoal, resin, or clay, or by distillation. Anyremaining monoglycerides in the ester phase may be removed with theglycerol layer by partial evaporation of alcohol from the reactionmixture.

Batch mode example: Generally, for batch mode reaction, a mixture ofalkyl alcohol, oil, and a catalyst is placed in a sealed autoclave andexposed to temperatures between 150° C. and 300° C., typically between180° C. and 230° C. for 30 to 120 minutes. The ratio of catalyst to oilshould be 1-10% by weight, and typically 2-6% by weight. The alcoholratio should be 1-10 volume equivalents, typically 3-8 volumeequivalents, most suitably 6 equivalents with respect to the amount ofoil present. After cooling and depressurizing, the reaction mixture isrecovered from the autoclave and filtered to remove the catalyst, whichmay be stored for later reuse. Excess alcohol is recovered bydistillation, and the alkyl ester product is recovered from residue bydecanting the separated glycerol.

Continuous/fixed bed example: Generally, oil and alcohol are fed atpredetermined fixed rates into a continuous fixed bed reactor containingthe desired mixed solid catalyst. The reactor is maintained at atemperature of 180° C. to 300° C., typically 180° C. to 230° C.depending on the catalyst used. Typical variables should be considered,including type and quality of feedstock, nature of alcohol, molar ratioof alcohol to oil, reaction time, temperature, pressure, and nature andquantity of catalyst.

Catalysts Examples

All reagents and alcohols used in the following examples were oftechnical grade. The triglyceride source/starting material was foodgrade canola oil with approximately 1% free fatty acids. All metaloxides, molecular sieves, and carboxylic acids were purchased fromAldrich Chemical Co. For free fatty acid reactions, hydrolyzed canolaand safflower oils were used as a source of free fatty acids. Reactionswere followed by thin layer chromatography and 400 MHz NMR. GC analyseswere performed following ASTM protocols on HP 6890 gas chromatograph.

Preparation of Catalyst MS-4 ÅK

Potassium exchanged molecular sieves were prepared by partial ionexchanging molecular sieves of molecular formula,Na₁₂[(AlO₂)₁₂(SiO₂)₁₂].xH₂O (MS-4 Å). 800 g of MS-4 Å were suspended in5000 ml, 0.5 Molar aqueous solution of potassium hydroxide and heatedunder reflux for 5 h and allowed to cool to room temp. The exchangedmolecular sieves were washed repeatedly to remove excess potassiumhydroxide from the molecular cages of the sieves.

Preparation of Catalyst MS-4 ÅCs

Cesium exchanged molecular sieves were prepared by partial ionexchanging molecular sieves of molecular formula,Na₁₂[(AlO₂)₁₂(SiO₂)₁₂].xH₂O (MS-4 Å). MS-4 Å (100 g) was suspended in700 ml, 0.5 Molar aqueous solution of cesium chloride and heated underreflux for 5 h and allowed to cool to room temp. The exchanged molecularsieves were washed repeatedly to remove excess cesium chloride from themolecular cages of the sieves.

Preparation of Catalyst MS-5 ÅK

Potassium and cesium exchanged molecular sieves were prepared by partialion exchanging molecular sieves molecular formula,Ca_(n)Na_(12-2n)[(AlO₂)₁₂(SiO₂)₁₂].xH₂O. MS-5 Å (100 g) was suspended in7000 ml, 0.5 Molar aqueous solution of cesium chloride and heated underreflux for 5 h and allowed to cool to room temp. The exchanged molecularsieves were washed repeatedly to remove excess cesium chloride from themolecular cages of the sieves.

Preparation of Catalyst MS-5 ÅCs

Cesium exchanged molecular sieves were prepared by partial ionexchanging molecular sieves of molecular formula,Ca_(n)Na_(12-2n)[(AlO₂)₁₂(SiO₂)₁₂].xH₂O. MS-5 Å (100 g) was suspended in700 ml, 0.5 Molar aqueous solution of cesium chloride and heated underreflux for 5 h and allowed to cool to room temp. The exchanged molecularsieves were washed repeatedly to remove excess cesium chloride from themolecular cages of the sieves.

Preparation of Catalyst C-I

Lanthanum chloride heptahydrate (25 g) was dissolved in water (100 ml)at room temperature and a mixture of a solution of potassium hydroxide(1M) and potassium carbonate (250 ml) was added over 1 h, whereupon awhite precipitate was formed. Resulting suspension was further stirredfor 1 hr; the solid was filtered, rinsed with 3×50 ml of 1:1 methanolwater mixture. The resulting solid was dried at 100° C. for 24 h andcalcined at 600° C. for 3 hours to get lanthanum oxide (Catalyst C-I).

Preparation of Catalyst C-II

Lanthanum chloride heptahydrate (15.2 g) in water (100 ml) was added toa solution of calcium chloride (30 g) in water (150 ml) at roomtemperature under vigorous stirring. A mixture of a solution ofpotassium hydroxide (1M, 200 ml) and potassium carbonate (0.5 M, 1000ml) was added under stirring over one hour, whereby a white precipitateis obtained. Reaction mixture was further stirred for one hour thenfiltered to recover a white solid, washed with 3×50 ml of 1:1methanol:water mixture. Solid was dried at 100° C. for 24 h and thencalcined at 600° C. for 3 hours to obtain lanthanum calcium oxide,x(La₂O₃).y(CaO) (where x=1 and y=3), hereinafter referred to as catalystC-II.

Preparation of Catalyst C-Ill

Lanthanum aluminum oxide, x(La₂O₃).y(Al₂O₃) (where x=2 and y=1)hereinafter referred to as catalyst C-III was prepared following theprocedure described catalyst C-II using aluminum chloride (17 g) andlanthanum chloride (25 g).

Preparation of Catalyst C-IV

Lanthanum zinc oxide, x(La₂O₃).y(ZnO) (where x=2 and y=1) hereinafterreferred to as catalyst C-IV was prepared following the proceduredescribed catalyst C-II using zinc chloride (17 g) and lanthanumchloride (25 g).

Catalysts C-V to C-XIV

Catalysts C-V to C-XIV were prepared by mixing required metal oxides andexchanged or un-exchanged molecular sieves from Table-1, respectively inwater to make a paste. The paste was extruded, dried at 100° C. for 24 hand calcined at 600° C. for 3 hours to obtain Catalysts from C-V toC-XIV (Table-1).

TABLE 1 Preparation of mixed metal oxide catalysts: Ms- Ms- Al₂O₃ ZnOTiO₂ La₂O3 La₂O₃•TiO₂ Fe₃O₄ Water 4ÅK 5ÅK Yield Catalyst (g) (g) (g) (g)(g) (g) (ml) (g) (g) (g) C-V 6.0 — — 9.8 — — — 11.5 — 25.2 C-VI 2.3 — —4.6 — — 8.0 2.3 — 8.9 C-VII 8.0 160 16.0 — — — 30.0 30.0 — 65.0 C-VIII30.0 300 30.0 — — — 200.0 250.0 — 295 C-IX — — — — 30.2 — — — — 29.7 C-X— 180 — — 18.0 — 40.0 30.0 — 60.0 C-XI 4.5 — — — 9.0 — 20.0 10.5 — 22.8C-XII — — — — — 20.0 — — — 20.0 C-XIII 3.0 3.0 3.0 — — 6.0 40.0 25.0 —37.5 C-XIV 3.6 8.2 8.2 — — — 25 — 13.4 32.8

Preparation of Catalyst C-XV

An aqueous solution of ammonium hydroxide (4 ml) was added drop wiseinto a stirred solution of 1.3 g of aluminum chloride dissolved in 5 mlof deionized water. To the resulting white suspension, a solution ofzinc oxide (0.9 g) in a solution of nitric acid (2.5 g) and water (7.5 Åml) was added and stirred to get a clear solution. This clear solutionwas absorbed on 3 molecular sieves of molecular formula,K_(n)Na_(12-n)[(AlO₂)₁₂(SiO₂)₁₂].xH₂O, (Ms-3 Å, 30 g) for one hour andthen dried at 100° C. for 5 hours. To this material at RT was addedammonium hydroxide solution (2 ml) and dried at 100° C. for 5 hours. Thematerial was calcined at 600° C. for 3 hours to give catalyst C-XV.

Preparation of Catalyst C-XVI

A solution of potassium hexacyanoferrate(II)-trihydrate (7.4 g, 17.5mmol) in 50 ml of water was added to lanthanum chloride heptahydrate(65.1 g) dissolved in a mixture of water (50 ml) and t-butanol (20 ml)at 50° C. over one hour. Reaction mixture was further stirred foradditional 18 h and cooled to ambient temperature. Separated solid wasfiltered, washed with a 3×40 ml of 1:1 mixture of water and t-butanol.It was dried at RT overnight, then at 60° C. under reduced pressure for5 h and finally at 170° C. for another 5 h to a constant weight. Driedmaterial having molecular formula Fe₂La₃(CN)₁₀, herein referred to ascatalyst C-XVI.

Preparation of Catalyst C-XVII

DMC catalyst C-XVII having molecular formula Fe₂Cu₃(CN)₁₀ was preparedusing hexacyanoferrate(II)-trihydrate (7.4 g) and copper(II)sulfate(55.9 g) following the method described for catalyst C-XVI.

Preparation of Catalyst C-XVIII

DMC catalyst C-XVIII having molecular formula Fe₂Al₃(CN)₁₀ was preparedusing hexacyanoferrate(II)-trihydrate (7.4 g) and aluminum chloride(23.3 g) following the method described for catalyst C-XVI.

Preparation of Catalysts C-XIX to C-XXI

Appropriate calcined metal oxides, a DMC and calcined Ms-4 ÅK were mixedtogether in desired quantities. Water (20 ml) was added to this physicalmixture to make a paste. The paste was extruded and dried at 100° C. for24 h and then at 170° C. for 5 h to a constant weight yielding catalystsC-IX to C-XXI, respectively. Compositions of catalysts C-IX to C-XXI arereported in Table 2.

TABLE 2 ZnO Ms-4ÅK Yield Catalyst DMC (g) Al₂O₃ (g) TiO₂ (g) (g) (g) (g)C-XIX C-XVI (1.5) 0.75 1.5 — 7.5 11.0 C-XX C-XVII(3.0) 1.5 3.0 — 15.023.0 C-XXI C-XVIII 0.75 1.5 — 7.5 11.3 (1.5) C-XXIII C-XXII(5.0) 3.0 5.05.0 36.0

Preparation of Catalyst C-XXII

DMC catalyst C-XXII having molecular formula Fe₂Zn₃(CN)₁₀ was preparedusing hexacyanoferrate(II)-trihydrate (7.4 g) and Zinc chloride (23.9 g)following literature-described methods.

Reaction Examples Batch Process for Transesterification of Canola Oil toBiodiesel

With respect to Table 3 below, a solid, mixed catalyst was placed with amixture of 10 g canola oil and 65 ml methanol in a 100 ml stainlesssteel autoclave equipped with a pressure gauge and pressure reliefvalve. The autoclave was sealed and heater in an oil bath at 200° C.±10°C. After cooling and release of pressure, the catalyst was recoveredfrom the reaction products and washed with methanol prior to reuse (andreactivated, if necessary). The filtrate, containing fatty acid methylester (FAME), glycerol, unreacted oil (if any) and methanol, wasseparated by evaporation and layer separation. Recovered methanol wasrecycled, glycerol removed, and the remaining oily products wereanalyzed. The results are presented in Table 3.

TABLE 3 Transesterification of canola oil using batch process Catalyst*   % Catalyst   $\left( \frac{{Catalyst}\mspace{14mu} (g) \times 100}{{Oil}\mspace{14mu} (g)} \right)$Time (h) % Conversion based on Triglyceride   consumption   1^(st)Use  2^(nd) Use ZnO 5.0 1.5 92.2 Al₂O₃ 5.0 1.5 90.4 34.0 TiO₂ 5.0 1.530.4 20.0 Ms-4ÅK 5.0 1.5 94.8 80.0 La₂O₃ 5.0 1.5 100 100 La₂O₃ 16.0 1.0100 100 C-II 5.0 1.5 100 100 C-III 5.0 1.5 100 100 C-IV 5.0 1.5 100 100C-V 5.0 1.5 97.4 100 C-VI 5.0 1.5 100 100 C-VII 5.0 1.5 95.6 62.6 C-VIII10.0 1.5 100 100 C-VIII 5.0 1.5 100 100 C-IX 5.0 1.5 98.3 83.5 C-IX 16.01.0 90.4 93.8 C-X 5.0 1.5 100 100 C-X 3.0 1.5 100 100 C-X 16.0 1.0 100100 C-XI 5.0 1.5 100 98.3 C-XII 5.0 1.5 71.3 48.7 C-XII 16.0 1.0 82.682.6 C-XIII 5.0 1.5 100 100 C-XIII 16.0 1.0 100 98.3 C-XIV 5.0 1.5 67.858.3 C-XIV 16.0 1.0 90.2 89.8 C-XV 5.0 1.5 40.9 27.0 C-XV 16.0 2.0 100100 C-XVI 5.0 1.5 97.4 100 C-XVII 5.0 1.5 54.8 63.5 C-XVIII 5.0 1.5 35.736.5 C-XIX 5.0 1.5 94.8 81.7 C-XX 5.0 1.5 100 81.7 C-XXI 5.0 1.5 59.137.4 C-XXIII 16.0 1.0 99.0 98.0 C-VIII 10 2.0 99.9 99.8 *Single metaloxides were calcined at 600° C. for 3 hrs prior to use

Batch Process for Esterification of Carboxylic Acids or Free Fatty Acids

With respect to Table 4 below, a mixture of a carboxylic acid or freefatty acids, and appropriate alcohol or phenol, and a catalyst wasplaced in a 100 ml stainless steel autoclave equipped with a pressuregauge and pressure relief valve. The autoclave was then sealed andheated in an oil bath for the time indicated, then cooled to ambienttemperature and pressure released. The reaction material was filtered torecover the catalyst, followed by washing of the catalyst in methanoland reactivation, if necessary. Methanol was removed by evaporation andthe residue was washed with bicarbonate solution to remove unreactedacid. Remaining solvent was removed by evaporation, and the recoveredester was analyzed by NMR and GC, with results shown in Table 4.

TABLE 4 Esterification of carboxylic acids Sr. Carboxylic Catalyst TimeConversion No Acid ROH Catalyst % (h) % 1 Free Fatty Acid MethanolC-VIII 10 1 100 prepared from Canola oil 2 Benzoic Acid Methanol C-X 101.5 100 3 Benzoic Acid Methanol C-VIII 10 2 100 3 2-Iodo BenzoicMethanol C-X 10 1.5 100 Acid 4 2-Iodo Benzoic Methanol C-VIII 10 1.5 100Acid

Continuous Fixed Bed Reactor Process for Transesterification of CanolaOil

A tubular stainless steel reactor, equipped with pressure regulator,back pressure control valve and thermometer, was filled with theindicated mixed solid catalyst. Canola oil and methanol were introducedat the indicated ratios and flow rates from bottom of the reactor usingtwo high pressure pumps. The reactor was heated externally such that thetemperature inside of the reactor was maintained between 200 and 250°C., and internal pressure was maintained between 350 to 1,000 psi,preferably between 400 to 650 psi. Hot effluents exiting from top of thereactor were flashed into an expansion chamber where methanol vapourswere separated, condensed and recycled. Residue liquid was drained intoa settling chamber where the lower layer (containing glycerol) wasseparated from the product. A series of continuous reactions wereconducted to optimize feed rate, temperature, pressure and contact timefor maximizing the conversion of oil into FAME and improving colour andquality of glycerol. The separated upper layer containing largely thebiodiesel product was analysed using NMR and GC to quantify FAME yieldand remaining oil if any. Results of runs using different catalysts arereported in Table-5.

TABLE 5 Fixed Bed Transesterification of Canola Oil CONTACT TEMP R H/APRESSURE TIME CONVERSION CATALYST ° C. VVH VOL/VOL PSI (MIN) (%) C-VIII200 0.5 1.0 650 60 99.8 C-VIII* 200 0.5 1.0 650 60 99.8 C-VIII 200 0.52.0 650 40 98.0 C-VIII 200 1.0 1.0 650 30 92.5 C-VIII 200 1.0 0.5 650 4095.0 C-VIII 200 0.75 0.5 650 60 98.3 C-VIII 230 0.75 0.5 650 60 99.8C-VIII 230 0.75 0.5 700 60 99.9 C-VIII 200 0.3 1.0 650 100 99.9 C-VIII200 0.25 1.0 650 120 99.9 C-VIII 200 1.5 1.0 650 40 95.0 C-VIII 215 1.51.0 650 40 97.0 C-VIII 200 2.0 1.0 650 15 80.0 C-VII 200 0.5 1.0 650 6099.8 C-VII 200 0.75 0.5 650 60 99.7 C-XXIII 200 0.5 1 650 60 97.0 C-III200 0.5 1 650 60 99.8 VVH = Volume of oil injected/volume of catalystper hr., R is ratio by volume of Oil/alcohol. *Recalcined catalyst afterseveral uses

The fixed bed reactor transesterification process may also be completedin two stages. This was carried out in cases where an incompleteconversion of triglycerides to FAME was noticed, or to increase theshift of reaction equilibrium, bringing the reaction to completion morequickly. The recovered upper layer from the reaction above was dilutedwith the desired quantity of methanol, and introduced into a secondreactor system with conditions similar to that described in Table 5.Effluents were concentrated and glycerol removed. Recovered FAME wasanalyzed using NMR and GC, with results reported below in Table 6.Catalyst beds were regenerated only if required, by heating at 600° C.for three hours except for catalysts containing DMC, which were heatedto 170° C. for five hours.

TABLE 6 Two-Stage Fixed Bed Transesterification of Canola Oil VVH VVHTemp Pressure Contact time Conversion % Stage-1 Stage-2 ° C. PSI Stage-1Stage-2 Stage-1 Stage-2 2 2 200 650 15 15 80 95.8 1 2 200 650 30 15 8295.8 2 1 200 650 15 30 80 93.3 1 1 200 650 30 30 82 99.9 VVH = Volume ofoil injected/volume of catalyst per hr., R is ratio by volume ofOil/alcohol.

The above-described embodiments of the present invention are intended tobe examples only. Alterations, modifications and variations may beeffected to the particular embodiments by those of skill in the artwithout departing from the scope of the invention, which is definedsolely by the claims appended hereto.

What is claimed is:
 1. A method for effecting esterification ortransesterification of a starting material, comprising reacting thestarting material with an alcohol in the presence of a solid,heterogeneous catalyst.
 2. The method as in claim 1, wherein thestarting material comprises an oil.
 3. The method as in claim 1, whereinthe starting material is selected from the group consisting oftriglycerides, free fatty acids, and a mixture thereof.
 4. The method asin claim 1, wherein the starting material comprises carboxylic acid. 5.The method as in claim 1, wherein biodiesel or a carboxylic acid esteris produced as a reaction product.
 6. The method as in claim 1, whereinthe method produces glycerol as a reaction product.
 7. The method as inclaim 1, wherein soap is not produced as a byproduct of the reaction. 8.The method as in claim 1, wherein the reaction is conducted attemperatures less than 250° C.
 9. The method as in claim 1, wherein thereaction is conducted at pressures less than 1000 psi.
 10. The method asin claim 1, wherein the reaction is conducted at pressures less than2000 psi.
 11. The method as in claim 1, wherein the reaction isconducted in a batch reactor.
 12. The method as in claim 1, wherein thereaction is conducted continuously using a fixed bed reactor.
 13. Themethod as in claim 1, wherein the reaction is conducted in one or moresuccessive stages.
 14. The method as in as in claim 1, wherein thereaction is conducted with a ratio of 0.1-2.0 volumes of injectedoil/volume of catalyst per hour.
 15. The method as in as in claim 1,wherein the solid, heterogeneous catalyst comprises at least onemodified molecular sieve, and at least one a metal oxide or double-metalcyanide.
 16. The method as in claim 15, wherein the metal oxide isaluminum oxide, calcium oxide, gallium oxide, hafnium oxide, iron oxide,lanthanum oxide, silicon oxide, strontium oxide, titanium oxide, zincoxide, or zirconium oxide.
 17. The method as in claim 1, wherein thesolid, heterogeneous catalyst is in powdered, pelleted, or extrudedform.
 18. The method as in claim 1, wherein the solid, heterogeneouscatalyst is recoverable from a batch reactor reaction product byfiltration.
 19. The method as in as in claim 1, wherein the solid,heterogeneous catalyst is according to the formulaa(La₂O₃).x(TiO₂).y(ZnO).z(MMS), wherein a and x are each 1; y is 1-2, zis 3-4, and wherein MMS is a modified molecular sieve obtained from thetype 3 Å, 4 Å, or 5 Å zeolite, having the general formulaK_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂]. x₁H₂O, Na₁₂[(AlO₂)₁₂(SiO₂)₁₂].x₁H₂O, or Ca_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂]. x₁H₂O, respectively,wherein x₁ has a value between 0 to 5 inclusive and n has a valuebetween 1 to 12 inclusive, modified by replacement of at least onesodium ion within an unmodified molecular sieve with at least one metalcation, wherein the MMS has the general formulaK_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂]. x₂H₂O,K_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂]. x₂H₂O,Cs_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂]. x₂H₂O, orCs_(m)Ca_(n)Na_({12-(m+2)})[(AlO₂)₁₂(SiO₂)₁₂]. x₂H₂O, wherein x₂ has avalue between 0 to 5 inclusive, and m and n independently have a valuebetween 1 to 12 inclusive.
 20. The method as in as in claim 1, whereinthe solid, heterogeneous catalyst is according to the formula(Al₂O₃).(TiO₂).(ZnO).z(MMS) wherein z is 10 and wherein MMS is amodified molecular sieve obtained from the type 3 Å, 4 Å, or 5 Åzeolite, having the general formula K_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂].x₁H₂O, Na₁₂[(AlO₂)₁₂(SiO₂)₁₂]. x₁H₂O, orCa_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂]. x₁H₂O, respectively, wherein x₁ hasa value between 0 to 5 inclusive and n has a value between 1 to 12inclusive, modified by replacement of at least one sodium ion within anunmodified molecular sieve with at least one metal cation, wherein theMMS has the general formula K_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂]. x₂H₂O,K_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂].x₂H₂O,Cs_(n)Na_((12-n))[(AlO₂)₁₂(SiO₂)₁₂]. x₂H₂O, orCs_(m)Ca_(n)Na_({12-(m+2n)})[(AlO₂)₁₂(SiO₂)₁₂].x₂H₂O, wherein x₂ has avalue between 0 to 5 inclusive, and m and n independently have a valuebetween 1 to 12 inclusive.